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Concentrations of 239Pu and 240Pu in 163 surface soil samples and five soil cores collected from the northeast and north China were analyzed using the radiochemical separation combined with inductively coupled plasma mass spectrometry measurement. The average 240Pu/239Pu atomic ratios (0.185 ± 0.018) for all surface soil samples indicated that the global fallout is the major source of plutonium in the studied region. The 239,240Pu concentrations of the surface soil ranged from 0.002 mBq/g to 4.82 mBq/g, lying in the range of the reported results in the areas with similar latitude, except for a few samples. The distribution of 239,240Pu in this region is controlled by the deposition of plutonium in the atmosphere and its preservation in the soil, which were affects by multi-factors such as topography, climate, utilization of the land and vegetation coverage. The analytical results could be used as the baseline data for the assessment of the impact of nuclear activities in the past and the future. [Display omitted] • Global fallout is the major source of plutonium in the Northeast China. • The topography and precipitation are key factor for the deposition of Pu. • The westerlies and monsoon are important for Pu distribution in north China. • Land use and vegetation are important for reservation of Pu in soil. [ABSTRACT FROM AUTHOR]

Transuranium elements such as Np, Pu and Am, are considered to be the most important radioactive elements in view of their biological toxicity and environmental impact. Concentrations of 237Np, Pu isotopes and 241Am in two sediment cores collected from Peter the Great Bay of Japan Sea were determined using radiochemical separation combined with inductively coupled plasma mass spectrometry (ICP-MS) measurement. The 239,240Pu and 241Am concentrations in all sediment samples range from 0.01 Bq/kg to 2.02 Bq/kg and from 0.01 Bq/kg to 1.11 Bq/kg, respectively, which are comparable to reported values in the investigated area. The average atomic ratios of 240Pu/239Pu (0.20 ± 0.02 and 0.21 ± 0.01) and 241Am/239+240Pu activity ratios (3.32 ± 2.76 and 0.45 ± 0.17) in the two sediment cores indicated that the sources of Pu and Am in this area are global fallout and the Pacific Proving Grounds through the movement of prevailing ocean currents, and no measurable release of Np, Pu and Am from the local K-431 nuclear submarine incident was observed. The extremely low 237Np/239Pu atomic ratios ((2.0–2.5) × 10−4) in this area are mainly attributed to the discrepancy of their different chemical behaviors in the ocean due to the relatively higher solubility of 237Np compared to particle active plutonium isotopes. It was estimated using two end members model that 23% ± 6% of transuranium radionuclides originated from the Pacific Proving Grounds tests, and the rest (ca. 77%) from global fallout. [Display omitted] • Distribution of transuranium radionuclides in the sediment cores were investigated. • The contribution of transuranium from PPG was estimated to be 23 ± 6 %. • No measurable release of transuranium from K-431 incident was observed. • 237Np/239Pu atomic ratio might be unsuitable for the source identification. [ABSTRACT FROM AUTHOR]